The present invention relates to a fluorine-containing surface active composition. More particularly, it relates to a novel fluorine-containing surface active composition which is effective in reducing the surface tension of water as well as the interfacial tension between water and oil.
In general, fluorine-containing compounds can reduce the surface tension of water and are useful as evaporation preventing agents, leveling agents, etc. On the other hand, there are considerable demands for additives for aqueous foam fire-extinguishing agents. Since it is necessary for such fire-extinguishing agents to spread quickly over an oil surface to form an aqueous film, the particular additives are required to have not only a capability of reducing the surface tension of water but also a capability of reducing the interfacial tension between water and oil. Namely, the spreading coefficient (S) has the relationship with the surface tension of oil (.gamma..sub.o), the surface tension of water (.gamma..sub.w) and the interfacial tension between water and oil (.gamma..sub.wo) whereby S=.gamma..sub.o -(.gamma..sub.w +.gamma..sub.wo), and water can spread over the oil surface only when S is positive. Unfortunately, however, the fluorine-containing group in conventional fluorine-containing compounds has only a low affinity to oil so that the satisfactory orientation at the interface between water and oil can not be attained. Thus, conventional fluorine-containing compounds can not sufficiently reduce the interfacial tension between water and oil. In order to supplement such insufficiency, the simultaneous use of a hydrocarbon compound surfactant is necessary.